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  #1  
Old 08-16-2007, 08:45 AM
Tonto Goldstein Tonto Goldstein is offline
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Default Film Production Sound Syncing from TC DAT - some thoughts

There are two severe limitations to Pro Tools that I would like to present to the DUC for comments. They are in regard to using PT to sync production sound to film dailies transferred to video tape (in this case Digital Betacam) for broadcast TV production.

First, some background: In the 90s I recorded production sound on a field DAT with 30fps Time-of-Day TC at 48.048kHz. I had a Sony PCM-7030 RS-422 controlled time code DAT deck for post. For every sync take we filmed a time code slate with a clapper backup. Synching transferred film takes was easy, using a standard video edit controller to do frame accurate audio insert edits to the Digi Beta or D2 deck containing the film transfer tape. The Sony DAT was set to resolve down to 48kHz, and a clean frame of the visual time code on the slate was used to set an in point on the DAT and the video transfer deck. An audio insert edit placed the DAT audio on the video tape tracks perfectly every time simply by entering the number seen on the slate image as the in point for the DAT.

But syncing in Pro Tools with time coded DAT source is another matter. The industry standard is to record time of day 30fps/ndf TC 48kHz DAT audio. The DAT tapes then must be loaded analog into Pro Tools using a .1% pullup and the TC set to 30fps. Time code is fed from the DAT to a Pro Tools Sync I/O and Pro Tools is placed in "online" record mode, where PT goes into record when the code from the DAT rolls and locks. Neither word clock (48.048kHz from the "pulled up" Pro Tools clock) nor video reference (29.97fps/59.94Hz) can be used as a reference timebase for the DAT as it is now running at 48kHz/30fps.

Once the raw production sound has been loaded in to Pro Tools one must turn off the pullup, change the TC rate to 29.97, and capture the video with a burn-in, place the resultant video files on the Pro Tools timeline, and align the sync takes with picture. Sounds simple enough.

But there are two problems:

1. When Pro Tools is placed into "online" record it drops out every time a time code break is encountered (i.e. every time the field recordist rolls for a new record). If I babysit the record button with the reflexes of a cat for the entire DAT tape I can usually hit record and it will resume chase-recording without needing to stop and rewind the DAT. Sometimes the field recordist records an erroneous short section of discontinuous time code and PT is unable to be put back into record and it instead starts chasing in play and can not be forced back into recording without stopping and rewinding the DAT. This is extremely annoying.

It would be great if Pro Tools could have a "contiuous" version of "record at TC lock" mode. Where you could just put in a TC DAT tape and walk away, and end up with a new time stamped file every time there is a TC break.

2. When dealing with Time of Day code one often encounters high hour numbers (oh, those long shoot days!!). But Pro Tools only has a 12 hour session limit. This is a problem.

In an ideal world my sycning session would consist of one or more "source" tracks with original DAT audio regions placed on the timeline at their original time stamp. These are at the Time of Day locations determined by the TC generator in the field DAT machine and are located for syncing by locating the Pro Tools cursor to the number seen on the TC slate before each take and generally start around 9 hours and go to whenever they last rolled for the day.

I also have a set of "destination" or sync tracks and a video track which are placed at the time code locations of the film rolls on the Digi Beta transfer reel. Since transfer reels are generally created with a new hour of TC for each film roll I can capture a whole tape with a burn in and, by doing video edits in Pro Tools, place the "chunks" of video on the PT time line so that the burn-in numbers align with Pro Tools.

I would prefer to create a syncing session that has my transfer reel video and resultant sync audio placement at the hours created by the transfer facility - roll 1 at 1:00hr, etc. and still have access to my raw DAT timestamped audio regions in the same session on my soruce tracks. Since most shoot days don't roll sound till around 9am and go till about 6 or 7pm or later it is obvious that a sync reel TC of 1:00hr start time and the last take of the day at, say, 22:08:15:19 Time-of-Day source TC would require a session length of 24 hours. The workaround to this is placing the video and sync track at a higher TC hour number and then changing the session start time in order to do a chase layback audio insert back to tape with of the synced audio.

The bigger picture is that film transfer facilities offer syncing of dailies to tape because they have telecines or edit controllers that can work directly from the DAT source, as described above. Since I work entirely in Pro Tools I have developed a fairly efficient method of syncing, but am frustrated by the lack of ability to digitize over time code breaks and by the limited 12 hour session length.

Finally, I might add that if the production crew use the simple acoustic clapper slate I really almost never even need the time code on the DAT. Clapper hits are readily visible on the Pro Tools waveform and I can load entire tapes without even bothering with DAT TC, find the clapper hits and break the source up into regions that are numberd with the slated take number, and go to work. Simply dragging the take region over the video track will quickly reveal the slate locations and once the clap frame is found the take region is dropped into place and the sync is complete. Old technology works better in this case. It is when the film crew only uses the TC visual slate and no clapper that the above applies exclusively.

And yes, I realize that a RS-422 TC DAT, an Avid, and an intern can probably sync more efficiently, but I would prefer to use my PT system for the many audio advantages it offers over Avid.

Your comments and feedback are appreciated.

goldstein_tonto@yahoo.com
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Old 08-16-2007, 11:19 AM
Frank Kruse Frank Kruse is offline
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Default Re: Film Production Sound Syncing from TC DAT - some thoughts

Quote:
But there are two problems:

1. When Pro Tools is placed into "online" record it drops out every time a time code break is encountered (i.e. every time the field recordist rolls for a new record). If I babysit the record button with the reflexes of a cat for the entire DAT tape I can usually hit record and it will resume chase-recording without needing to stop and rewind the DAT. Sometimes the field recordist records an erroneous short section of discontinuous time code and PT is unable to be put back into record and it instead starts chasing in play and can not be forced back into recording without stopping and rewinding the DAT. This is extremely annoying.

Just set PT to "transport lock" and "record-lock" PT will then go into record again automatically a few seconds after each TC-break.


Quote:

2. When dealing with Time of Day code one often encounters high hour numbers (oh, those long shoot days!!). But Pro Tools only has a 12 hour session limit. This is a problem.


Indeed. Do not record free-run TOD if you want to do this. Record in record-run unless you´re jam-synced to smart-slates or cameras.
If you are using simple clapper-boards there is no real reason to record in record-run mode. Your telecine and avid-operator will also be hapier if they receive continuous TC on the DAT.

Frank.
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Old 08-16-2007, 12:08 PM
Tonto Goldstein Tonto Goldstein is offline
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Default Re: Film Production Sound Syncing from TC DAT - some thoughts

Frank,
Wasn't aware of "transport lock" or "record lock"...will re-investigate. Thanks for the info.

Re: Record run TC on the location deck: Yes, that would be great, but I am not the one doing the recording on location. That would certainly eliminate the high hour numbers but people love their TOD TC. Often when rolling a multitrack with multiple cameras the only sensible method is free-running TOD TC where the slates are jammed from the sound recorder and then walk away. Using record run TC on the audio 'master' would require a hardwire or wireless link to the slates and/or film cameras. Doable but often not practical and god forbid there be a TC problem caused by the sound department. (Sets can grind to a halt because the DP wants to ad light number 75, but if Sound causes even a second of delay there are a chorus of groans from the crew!).

Thanks again for your feedback!

Shaun
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Old 08-16-2007, 12:23 PM
Tonto Goldstein Tonto Goldstein is offline
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Default Re: Film Production Sound Syncing from TC DAT - some thoughts

NEVER MIND on the time code break problem - Frank was right, I just tried it. Who knew? I looked in the manual under every description I could think of except "transport lock".

Yeah Frank!!!
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  #5  
Old 08-16-2007, 01:21 PM
Frank Kruse Frank Kruse is offline
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Default Re: Film Production Sound Syncing from TC DAT - some thoughts

Quote:
Often when rolling a multitrack with multiple cameras the only sensible method is free-running TOD TC where the slates are jammed from the sound recorder and then walk away. Using record run TC on the audio 'master' would require a hardwire or wireless link to the slates and/or film cameras.Shaun
Yes, I kow. You wrote that you´re using regular slates, no TC. That´s why I mentioned this. Of course jam-synced machines don´t allow record-run tc.


frank.
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